Packet networks such as IP, Ethernet, ATM, FC (Fiber channel) operate according to protocols defining burst-like transmission of information units called packets or cells, wherein the length and contents of the packets in each specific network are predetermined by the suitable standards and protocols.
The Ethernet network protocol was one of the first protocols developed for packet networks, and initially was designed for serving local area networks (LANs) where the problem of signaling was not critical at the time. The Ethernet signaling mechanism which was originally designed comprises a so-called “auto-negotiation” mechanism. Though, it is not sufficient for many novel requirements which modern networks impose.
Presently, not only the modern LANs grew, but as a rule, they are now interconnected by wide area networks (WANs) which operate according to totally different protocols. That is a result of one of the trends in the modern world of communications where integration of various types of networks becomes more and more popular. For example, a communication path between two end users or providers may include both network sections utilizing packet framing (such as IP or Ethernet), and sections of optical networks such as SDH or SONET utilizing so-called virtual containers which are complex aggregated structures of digital frames. For transmitting Ethernet packets, digital frames of SONET/SDH envelope the information comprised in the Ethernet packets (SONET/SDH is generally considered a lower level, and Ethernet—a higher level).
It should be noted that SONET and SDH networks support a wide range of signaling and checking means. For example, SDH and SONET protocols comprise a set of functions of a so-called Tandem Connection feature (SDH TC feature). One of such functions serves to distinguish errors which appear in a particular network domain path enclosed between a Source and a Sink of its Tandem Connector, from external errors received by the domain with the incoming information flow. On the other hand, such tools are designed for virtual containers and cannot specify errors taking place at any higher layer, say in Ethernet packets contents of which is mapped in the “carrier” virtual container frames. It means that information provided by the SDH TC feature is insufficient for revealing sources of errors and handling associated problems if they reside in the packet network sections.
According to the a Standard recommendation of an International Telecommunication Union ITU-T I.610 (February 1999), Asynchronous Transfer Mode networks are provided with so-called Operation And Maintenance functions (OAM functions) for performance monitoring, defect and failure detection/information, system protection and fault localization. For accomplishing the performance monitoring, maintenance information is produced from user information; this maintenance information is added to the user information at the source of a connection/link and extracted at the sink of a connection/link. Analysis of the maintenance event information at the sink of the connection allows estimation of the transport integrity.
To the best of the Applicant's knowledge, none of the presently known standard recommendations, patent documents or other sources describes or suggests any signaling means for monitoring Ethernet packets when transmitted via any network domain, in particular via a SONET or SDH network.